Pool losing water on filter but not recirculate

[CarlD]

Two immediate thoughts spring to mind, and both involve the multi-valve.
1) There may be a broken partition between chambers.
2) The spider gasket may be defective, damaged, or installed wrong.

There could be other causes but either of those COULD cause the problem.

You could also have a leak somewhere in your sand tank. On RECIRCULATE, the water doesn't flow through the tank. Check the drain valve first--is there water under the tank?

[Aerobatty]

Thanks for your reply. There's no water around the tank. It's bone dry. I took the backwash hose off to make sure it's not leaking through there. I'm trying to do longer checks on each cycle, but we've been getting rain that doesn't help. I think I'm eventually going to have to replace the return fixtures again.